I need to cut a 1inch hole in the bottom of my hull (!)

[MapisM]

My money is on JFM getting them in.
Structure Scan is a very different animal to Echopilot and, having seen it working first hand, think the OP will be very impressed.

Never seen it working, but from what I've read about it, you might well be right.
Provided that it's used at D speed of course, but I guess CMJ is already aware of that, since he mentions "<10kts".

 

[CMJ]

Many thanks.....

......to everyone who's replied - really appreciated and very helpful - has given me confidence to go ahead and cut the hole

 

[CMJ]

No No, it must be drilled so the transducer is pointing straight down, (pilot hole from the inside first) the fairing block is then cut with a bandsaw to compensate for the angle. Don't worry, it's all in the instructions that come with the unit including which sealent to use, how to deal with cored hulls etc etc.

That makes sense.

So, I'm definitely going to cut the hole now (prob next weekend) - the next thing I need to work out is where? There is a perfectly flat section at the lowest part of the hull that is wide enough to take the transducer - so would simplify installation, but my two concerns are:

1) if I put it in the 'ideal' place - i.e a couple of feet ahead of the raw water intakes then if I grounded the boat then there's an increased risk of damaging / ripping off the transducer exposing the hole!

2) if I put it in-between the two raw water intakes, then will turbulence around the intakes affect this readings? - the plus is that the transducer would be 'protected' by the intakes - but another disadvantage is whether the intakes will be in the line of sight of side-scanning (I need to check).

I plan to use sikaflex 291 and a hole saw - probably this one

I've read that sometimes the sealer is left to slightly cure before fully tightening, so that it's not totally squeezed out between the faces - but I'm unsure whether to do this or not as tightening the nut might shear the sealant in the actual hole as the transducer is pulled towards the hull - I suspect the sealer is far too elastic for this to happen but just a thought...

 

[MapisM]

1) if I put it in the 'ideal' place - i.e a couple of feet ahead of the raw water intakes then if I grounded the boat then there's an increased risk of damaging / ripping off the transducer exposing the hole!

I'd go for that. After all, the whole purpose of the thingie is to avoid grounding, innit?

 

[CMJ]

After all, the whole purpose of the thingie is to avoid grounding, innit?

You'd think so I agree! But, actually it's to satisfy my fascination as to what's underneath me in the water rather than a tool to detail current depths etc (and it's not forward looking).

 

[CMJ]

The Hole....

Ok, I plucked up the courage last week and cut the hole to fit the transducer – I placed just forward of the existing depth sounder, and knowing they operate at different frequencies, hopefully there’ll be no interference between them.
Cutting the hole was easier that I thought it might be and within minutes, there was a hole – eeek!


This first pic shows the thickness of the hull (15mm) – a bit thinner than I thought it might be so better avoid the rocks!! Also proves that the hull is not cored.

Next pic shows cut hole

And here’s my mate Steve sat inside the engine room pulling the cable though for me

And lastly, the installed transducer – pretty sure I used too much sikaflex, as had loads and loads squidge out the sides, but I guess better too much than too little!

It will probably be a few weeks before I connect everything up but will post some pics of the ‘StructureScan’ running when done in hope to claim a cold beer off JFM